Synthesis of Optically Active β′-Hydroxy-β-enaminoketones via Enzymatic Resolution of Carbinols Derived from 3,5-Disubstituted Isoxazoles.

Abstract The preparation of several enantiomerically pure β′-hydroxy-β-enaminoketones from the corresponding isoxazolic carbinols, which have been obtained by enzymatic kinetic resolution of the racemic β-hydroxyisoxazoles catalyzed by lipases, is described. The enzymatic transesterification of racemic (±)-5-(2-hydroxypropyl)-3-methylisoxazole 3a , and racemic (±)-5-(2-hydroxy-2- p -tolylethyl)-3-methylisoxazole 3d , has been studied with respect to the influence of experimental variables such as the used enzyme, the acylating agent or the solvent on the enantioselectivity of the reaction. After the reductive cleavage of the isoxazolic ring of the enantiopure carbinols, ( R )- and ( S )-2-amino-4-oxo-2-hepten-6-ol , ( R )- and ( S )- 5 , and ( R )- 2- amino-6- p -tolyl-4-oxo-2-hexen-6-ol, ( R )- 7 with an enantiomeric excess >98% were obtained.